Montelukast

Montelukast is approved for several breathing and allergy conditions; the specific form and age group determine which uses apply.

• Asthma (long-term prevention and treatment): Tablets for patients 15 years and older; chewable tablets for patients 2 years and older; Montelukast Sodium and Singulair oral granules for patients 12 months and older.
• Exercise-induced bronchoconstriction (acute prevention): Tablets and chewable tablets for patients 6 years and older (tablets labeled for 15+ years in some products). Oral granules are not indicated for this use.
• Seasonal allergic rhinitis (hay fever): Tablets for patients 15 years and older; chewable tablets for patients 2 years and older; Montelukast Sodium and Singulair oral granules for patients 2 years and older.
• Perennial allergic rhinitis (year-round nasal allergies): Tablets for patients 15 years and older; chewable tablets for patients 2 years and older; Singulair and Montelukast Sodium oral granules for patients 6 months and older.
• Important limitation: Montelukast is not used to treat a sudden asthma attack. For allergic rhinitis, it should only be used when other treatments haven't worked or are not tolerated.

Your body produces inflammatory chemicals called leukotrienes during allergic reactions. These leukotrienes attach to a receptor in the airways and nose called the CysLT1 receptor, causing swelling, airway tightening, and excess mucus — the hallmarks of asthma and allergic rhinitis. Montelukast selectively blocks that receptor, preventing leukotrienes from triggering those effects and helping to keep airways open and nasal passages calmer.

In clinical studies, montelukast reduced a type of inflammatory white blood cell (eosinophils) in the blood of people with asthma, and blunted both the early and late phases of allergen-triggered airway narrowing — suggesting it works on more than one stage of the allergic response.

Montelukast is taken by mouth once daily. For asthma and year-round or seasonal nasal allergies, it is typically taken in the evening; for seasonal allergic rhinitis treated with the tablet form, morning or evening dosing has been studied. For preventing exercise-related breathing problems, it is taken as a single dose at least 2 hours before exercise. Patients who have both asthma and allergic rhinitis should take only one dose per day, in the evening.

• Tablets can be taken with or without food.
• Chewable tablets can be taken with or without food, though a standard meal may affect how much is absorbed.
• Oral granules (powder form) must be taken within 15 minutes of opening the packet; they can be taken alone or mixed with a small amount of soft food like applesauce.

Always follow your prescriber's exact instructions and the directions on your prescription label.

The most common side effects reported in clinical trials include:

• Upper respiratory infection (cold symptoms)
• Headache
• Fever
• Sore throat (pharyngitis)
• Cough
• Stomach pain
• Diarrhea
• Sinus congestion or sinus infection

More serious reactions — including severe mood or behavior changes, signs of liver injury (yellowing of skin or eyes, severe stomach pain), severe allergic reactions (hives, facial swelling, difficulty breathing), or unusual skin reactions — require immediate medical attention. If you notice any thoughts of self-harm or suicide, stop montelukast and call your doctor or emergency services right away.

• Serious mental health and behavior changes (Boxed Warning): Montelukast has been linked to agitation, aggression, depression, hallucinations, sleep disturbances, and suicidal thoughts or actions. This can happen in adults, teenagers, and children, even in those with no prior mental health history. Stop montelukast and contact a doctor immediately if these symptoms appear.
• Not for acute asthma attacks: This medicine does not work fast enough to reverse sudden bronchospasm. Always have a fast-acting rescue inhaler available.
• Do not abruptly replace steroids: If you're on inhaled or oral corticosteroids, do not suddenly switch to montelukast — the dose should be reduced gradually under medical supervision.
• Aspirin and NSAID sensitivity: If you're known to be sensitive to aspirin or NSAIDs, continue avoiding them while on montelukast — it does not protect against those reactions.
• Churg-Strauss syndrome (rare): A rare condition involving blood vessel inflammation has been reported, sometimes in people whose oral steroid doses were being reduced. Watch for worsening lung symptoms, skin rash, or numbness/tingling.
• Phenylketonuria (PKU): The chewable tablet form contains phenylalanine and must be used with caution in people with PKU.

Montelukast has been studied alongside many common medications and generally does not require dose adjustments. Key points:

• Corticosteroids (prednisone, prednisolone, inhaled steroids): No dose change needed, but do not abruptly stop steroids when starting montelukast.
• Warfarin (blood thinner): No dose adjustment needed, but your prescriber should still monitor as usual.
• Theophylline: No dose adjustment needed.
• Digoxin: No dose adjustment needed.
• Oral contraceptives: No dose adjustment needed.
• Gemfibrozil and itraconazole (affect liver enzymes): No dose adjustment needed.
• NSAIDs and aspirin: No pharmacokinetic interaction, but aspirin-sensitive patients must still avoid them.
• Sedative sleep aids and benzodiazepines: No dose adjustment needed.

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Allergic to montelukast or any of its ingredients: Do not take — it is contraindicated.
• History of depression, anxiety, or other mental health conditions: Discuss the risks carefully with your prescriber before starting.
• Phenylketonuria (PKU): The chewable tablet form contains phenylalanine — discuss with your doctor before use.
• Pregnant: Available data from studies in pregnant women have not shown a clear risk of major birth defects, but poorly controlled asthma in pregnancy carries its own risks. Discuss with your doctor.
• Breastfeeding: Montelukast is present in breast milk. Weigh the benefits of breastfeeding against any potential risk and consult your doctor.
• Children: Safety and effectiveness vary by form and age group — some forms are approved for infants as young as 6 months, others only for patients 15 and older. Confirm the appropriate product with your prescriber.
• Older adults (65+): No dose adjustment needed; however, some older individuals may be more sensitive. Monitoring is recommended.
• Liver disease (mild to moderate): No dose adjustment needed.
• Kidney disease: No dose adjustment needed.

There is no specific antidote for a montelukast overdose. If too much is taken, standard supportive care is recommended — including removing any unabsorbed medication from the stomach and monitoring the person closely. It is not known whether dialysis removes montelukast from the body. If you suspect an overdose, call Poison Control or go to the nearest emergency room.

Montelukast blocks the CysLT1 receptor in the airways, measurably reducing airway narrowing triggered by inhaled leukotrienes. In studies with people with asthma, it blunted the early-phase allergic airway response by about 75% and the late-phase response by about 57%. In patients with asthma, it also reduced levels of eosinophils (an inflammatory cell type) in the blood by roughly 9–15% compared to placebo. In patients with seasonal allergic rhinitis, it substantially reduced the normal allergy-season rise in blood eosinophils seen in placebo-treated patients.

Montelukast is absorbed quickly after being swallowed, with peak blood levels reached within 2 to 4 hours depending on the form taken. It is more than 99% bound to proteins in the blood and is processed primarily by the liver. About 86% of the drug leaves the body through the stool, with very little excreted in the urine. The oral granule form can be taken with soft foods like applesauce without significantly affecting overall absorption, though a high-fat meal may delay the time to peak levels. The drug's clearance is slightly slower in older adults, but no dose adjustment is needed.

Store SINGULAIR 4-mg oral granules, 4-mg chewable tablets, 5-mg chewable tablets and 10-mg film-coated tablets at 20°C to 25°C (68°F to 77°F), excursions permitted to 15°C to 30°C (59°F to 86°F) . Protect from moisture and light. Store in original package.